This invention relates to the problem of the partial or complete blockage of the mechanism, when dispensing dry particulate `solid` materials in agriculture or industry with existing distribution devices. `Solid` material in this context is generally in either crystaline, powder, granular or prill form.
In real terms, the actual physical form of any one class of solid particulate material contains a range of particle sizes, sometimes falling well outside that of the manufacturer's specification, and also the ambient conditions pertaining at the time of operation can cause moisture to be picked-up or be absorbed by the solid material causing it to become agglomerated, caked or crusted. Calibration of the device is invariably upset, even to the extent that, at times, no material at all may be supplied through the outlet through which particulate material is supposed to issue as the device operates.
This problem is further aggravated by the difficulty in cleaning out the mechanism of the majority of agricultural distributors known by the present inventor to be actually in production. Cleaning out conventional distributors invariably involves the removal of the entire contents of the hopper or bin before access is obtained to the mechanism situated at the lowest point and in many cases, the distributor mechanism itself has to be dismantled before the bottom surface of the hopper can be reached.
Moisture can cause the fine particles to form an accretion on the inner bottom surface of the hopper, which accretion is so hard that only hammer and chisel action can effect removal.
The screens commonly fitted near the bottoms of hoppers in existing particulate material distributors are of little use in coping with over-sized material, and lumps are common-place when bagged material is stored for lengthy periods in adverse conditions and then dumped into the hopper of the distributor. Should the screen become blocked by lumps, the whole hopper has to be emptied to clear the blockage. Screens at the top of the hopper hinder refilling of the hopper and cause spillage, as well as being an additional item requiring removal when a clean-out is necessary.
It is known to the inventor that certain attempts have been made to overcome the abovementioned drawbacks, all having had but a limited degree of success. By way of example, the provision of a clean-out door with a hinged metal flap at the bottom of the hopper is known, which will allow access to the distributor mechanism under the hopper. That prior art system in itself has a number of drawbacks which it is hoped will be overcome by the present invention. For example, no matter how well formed it is, the metal flap does not effectively seal the base of the hopper and material wastage can occur with resultant inaccuracies in distribution. The metallic materials used in making this part of the housing are prone to corrosion and may furthermore become distorted and damaged by rough or otherwise incorrect handling.